Coupled Effect of Cementation Solution, Curing Period, Molding Water Content, and Compactive Effort on Strength Performance of Biotreated Lateritic Soil for Municipal Solid Waste Containment Application

Abstract

Microbial-induced calcite precipitation (MICP) is a soil improvement technique that has shown great potential in several geotechnical applications in the previous decade. Some factors that led to the improved strength included cementation concentration. The combined influence of these factors with the cementation reagent was paramount to the calcite precipitation level within soil grain contact of a biotreated compacted fine-grained soil. In this study, the influence of the concentration of the cementation solution [(CCS) 0.25, 0.5, 0.75 and 1.00 M], curing time [(CT) 24 h, 3, 7, 14, and 28 days], and molding water content [MWC (9.8%–19.6%)] of biomediated lateritic soil or lateritic soil that was bioinfused with ureolytic microbes at different suspension densities (cells/mL) and compacted with Reduced British Standard Light (RBSL), British Standard Light (BSL), West African Standard (WAS), and British Standard Heavy (BSH) energy, respectively, were evaluated. In addition, this study focused on unconfined compressive strength (UCS). The results showed an increased UCS with the corresponding average calcite content up to peak values at 0.5 M cementation concentration for the five considered bacterial cells/mL. In addition, the results showed a linear relationship between UCS and average calcite content for the CCS that were considered. The effect of the curing period on UCS was marginal within individual cementation concentrations regardless of bacterial cells/mL. The UCS of the specimen that contained the optimal 0.5 M cementation concentration increased with higher bacterial cells/mL but decreased with the MWC. The qualitative microanalysis that used scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses that evaluated the untreated and biotreated specimens showed the formation of calcite, which increased the soil strength by blocking the soil pores through grain–grain contacts.